Chris Rea's scheduled concert in Brighton on Sunday will not go ahead following the singer's collapse on Saturday evening.
The Driving Home For Christmas singer had been performing at the New Theatre in Oxford when he fell to the stage mid-song, with one audience member describing him "falling into a clump".
Currently in the midst of his The Road Songs For Lovers live tour, he was scheduled to perform at the Brighton Centre on Sunday, but this has now been cancelled.
Shortly after the incident on Saturday night, Rea was thought to be in a "stable" condition.
The 66-year-old suffered a stroke last year.
The Brighton Centre said in a tweet that "tickets will be refunded at point of purchase".
Darren Fewins, who had been watching the show with his wife, told the Press Association the musician had been on stage for 40 to 45 minutes before he fell backwards.
"He was standing by the microphone and he had the guitar in his hand and he kept shaking his left hand as if there was something not quite right with it," the 46-year-old said.
"He walked forward to the microphone and he was trying to grab the microphone with his left hand, and it was swinging from side-to-side.
"I thought at first there was something wrong with it and he was trying to keep it steady. He then took three or four steps backwards.
"Then he just collapsed on the stage backwards. There was no-one there to catch him, he just fell into a clump.
"He was on his back for about two minutes before they brought the curtain down and then that was it."
Another audience member said Rea had been "slurring his words a lot through the song beforehand".